Cogeneration device

ABSTRACT

A cogeneration system is provided which includes a prime mover for obtaining power for driving a generator by combustion of a fuel, a waste heat boiler for recovering thermal energy from exhaust gas discharged from the prime mover, and a heat exchanger for heating air that is to be fed into an air conditioner by heat exchange with the exhaust gas discharged from the waste heat boiler. Drain water that is generated from the exhaust gas cooled by heat exchange in the air-heating heat exchanger ( 5 ) with the air that is to be fed into the air conditioner ( 30 ) is recovered by drain water recovery/supply means ( 36 ). The drain water recovery/supply means ( 36 ) supplies the drain water thus recovered to appliances ( 37, 38 ) that require comparatively high temperature water. Thermal energy can thus be recovered effectively from the drain water discharged from the heat exchanger on the downstream side of the waste heat boiler, thereby improving the efficiency of recovery of waste heat energy.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a National Stage entry of International ApplicationNo. PCT/JP02/00385, filed Jan. 21, 2002. The disclosure of the priorapplication is hereby incorporated herein in its entirety by reference.

FIELD OF THE INVENTION

The present invention relates to a cogeneration system that includes aprime mover for obtaining power for driving a generator by combustion ofa fuel, a waste heat boiler for recovering thermal energy from exhaustgas discharged from the prime mover, and an air-heating heat exchangerfor heating air that is to be fed into an air conditioner by heatexchange with the exhaust gas discharged from the waste heat boiler.

BACKGROUND ART

Such a cogeneration system is known from, for example, Japanese PatentApplication Laid-open No. 4-342807 in which, after the thermal energy ofexhaust gas discharged from a prime mover is recovered by a waste heatboiler, air that is to be used in an air conditioner is heated by heatexchange with the exhaust gas in an air-heating heat exchanger, thusrecovering the waste thermal energy effectively.

In the air-heating heat exchanger, which carries out heat exchange withthe exhaust gas on the downstream side of the waste heat boiler, part ofthe water contained in the exhaust gas is condensed by being cooled byheat exchange with the air that is to be fed into the air conditioner,and is discharged as drain water, and although the temperature of thedrain water is expected to be comparatively high, there is noconventional system in which the thermal energy is recovered effectivelyfrom such drain water.

DISCLOSURE OF THE INVENTION

The present invention has been achieved in view of the above-mentionedcircumstances, and it is an object thereof to provide a cogenerationsystem that recovers thermal energy effectively by acquiring drain waterduring heat exchange between exhaust gas discharged from a waste heatboiler and air that is to be used in an air conditioner, thus improvingthe efficiency of recovery of the waste thermal energy.

In order to achieve this object, in accordance with a first aspect ofthe present invention there is provided a cogeneration system thatincludes a prime mover for obtaining power for driving a generator bycombustion of a fuel, a waste heat boiler for recovering thermal energyfrom exhaust gas discharged from the prime mover, and an air-heatingheat exchanger for heating air that is to be fed into an air conditionerby heat exchange with the exhaust gas discharged from the waste heatboiler, characterized in that the system includes drain waterrecovery/supply means capable of recovering drain water generated fromthe exhaust gas cooled by heat exchange in the air-heating heatexchanger with the air that is to be fed into the air conditioner andsupplying the drain water thus recovered to an appliance that requirescomparatively high temperature water.

In accordance with the arrangement of the first aspect, the drain waterrecovered from the air-heating heat exchanger is utilized in theappliance that requires comparatively high temperature water, thusimproving the efficiency of recovery of the waste thermal energy. Thatis, in the case where room temperature water is used, a heater isrequired, but since comparatively high temperature drain water can besupplied, consumption of extra energy can be avoided.

Furthermore, in accordance with a second aspect of the presentinvention, in addition to the first aspect, there is provided acogeneration system wherein the system further includes a pure watergenerator for generating pure water for supply to the waste heat boiler,and a waste-water-heating heat exchanger for heating waste water fromthe pure water generator by heat exchange with the exhaust gasdischarged from the waste heat boiler, the drain water recovery/supplymeans including a tank in which the waste water heated by thewaste-water-heating heat exchanger and the drain water are mixed. Inaccordance with this arrangement, even when the drain water generatedfrom the exhaust gas is alkaline, since the alkalinity can be weakenedby dilution due to the mixing with the waste water from the pure watergenerator within the tank, its application can be extended by enablingthe water within the tank to be utilized effectively in more appliances.

Moreover, in accordance with a third aspect of the present invention, inaddition to the second aspect, there is provided a cogeneration systemwherein the drain water recovery/supply means is arranged so as to beable to recover drain water generated from the exhaust gas cooled byheat exchange with the waste water in the waste-water-heating heatexchanger, and to supply the drain water to the appliance. In accordancewith this arrangement, the water contained in the exhaust gas can berecovered more effectively, thereby further improving the efficiency ofrecovery of the waste thermal energy.

Furthermore, in accordance with a fourth aspect of the presentinvention, in addition to the second or third aspect, there is provideda cogeneration system wherein a bypass that bypasses the air-heatingheat exchanger and switches over between opened and closed statesaccording to the outside air temperature is connected, on either side ofthe air-heating heat exchanger, to an air conditioner air supply passageconnected to the air conditioner. In accordance with this arrangement,changes according to the season in the amount of drain water and thetemperature of the air conditioner that are required can beaccommodated.

Moreover, in accordance with a fifth aspect of the present invention, inaddition to the first or third aspect, there is provided a cogenerationsystem wherein the appliance is an air conditioner air humidifier. Inaccordance with this arrangement, the water contained in the exhaust gascan be recovered effectively and used in the air conditioner airhumidifier.

Furthermore, in accordance with a sixth aspect of the present invention,in addition to the first or third aspect, there is provided acogeneration system wherein the appliance is a hot water washer. Inaccordance with this arrangement, the water contained in the exhaust gascan be recovered effectively and used in the hot water washer.

Moreover, in accordance with a seventh aspect of the present invention,in addition to any one of the first to sixth aspects, there is provideda cogeneration system wherein the waste heat boiler is connected to acombustor of a gas turbine, which is the prime mover, to thereby supplya part of steam acquired by the waste heat boiler to the combustor. Inaccordance with this arrangement, by increasing the weight of a gas fedto the turbine via the combustor and increasing the rotational speed ofthe turbine, the capacity of the generator can be increased, and thesteam returned to the gas turbine can be recovered effectively as drainwater.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 and FIG. 2 illustrate one embodiment of the present invention;FIG. 1 is an overall schematic diagram of a cogeneration system; andFIG. 2 is a schematic diagram showing the arrangement of a generatorsystem.

BEST MODE FOR CARRYING OUT THE INVENTION

Modes for carrying out the present invention are explained below byreference to one embodiment of the present invention illustrated in FIG.1 and FIG. 2. Referring firstly to FIG. 1, exhaust gas discharged from agenerator system 1 is directed to a stack 2. The induction side of aninduction fan 4 is connected to the stack 2 via an open/close valve 3,and the discharge side of the induction fan 4 is connected to a stack 7via an air-heating heat exchanger 5, and a waste-water-heating heatexchanger 6 connected to the downstream side of the air-heating heatexchanger 5.

In FIG. 2, the generator system 1 includes a gas turbine 8, which is aprime mover, a generator 9 that is driven by the gas turbine 8, and awaste heat boiler 10 that recovers thermal energy by heat exchange withexhaust gas discharged from a combustor of the gas turbine 8. Theexhaust gas discharged from the waste heat boiler 10 is directed to thestack 2.

The gas turbine 8 includes a turbine 11, a compressor 12 coaxiallyconnected to the turbine 11, and the combustor 13. Supplied to thecombustor 13 are air pressurized by the compressor 12, a fuel gas suchas town gas compressed by a gas compressor 14, and also a part of steamacquired by the waste heat boiler 10.

An exhaust gas containing steam is discharged from the combustor 13 as aresult of combustion of the fuel gas in the combustor 13, this exhaustgas rotates the turbine 11 to drive the generator 9, and a combustionexhaust gas discharged from the turbine 11 is directed to the waste heatboiler 10 .

This waste heat boiler 10 includes a heater 15, a denitration device 16,and a preheater 17. The heater 15 heats part of the steam acquired bythe waste heat boiler 10 by heat exchange with the exhaust gas from theturbine 11.

The steam heated by the heater 15 is supplied to the combustor 13 of thegas turbine 8. The denitration device 16 is arranged such that air fedby a blower 18 and ammonia supplied by a pump 20 from an ammonia tank 19are sprayed via a plurality of nozzles 21, 21 into the waste heat boiler10. NO_(x) present in the exhaust gas from the combustor 13 and ammonia(NH₃) react with each other as in (NO_(x)+NH₃=N₂+H₂O) to thereby removeas much NO_(x) as possible from the exhaust gas.

The preheater 17 is provided in the waste heat boiler 10 on thedownstream side of the denitration device 16; pure water fed by a pump23 from a pure water tank 22 is heated by heat exchange with the exhaustgas in the preheater 17, and supplied to the waste heat boiler 10. Purewater, from which calcium content is removed by a pure water generator26, is supplied by a pump 27 to the pure water tank 22. NaOH is suppliedby a pump 25 from a caustic soda tank 24 to the pure water that is to besupplied to the preheater 17 by the pump 23. This NaOH functions toprotect the wall of the waste heat boiler 10 when the steam generated inthe waste heat boiler 10 reaches the waste heat boiler 10 via thecombustor 13.

In this way, in the generator system 1, part of the thermal energy ofthe exhaust gas discharged from the combustor 13 of the gas turbine 8 isrecovered by converting the pure water into steam in the waste heatboiler 10. Part of the steam acquired by the waste heat boiler 10 issupplied to the combustor 13 as described above, and the remainder ofthe steam is used as plant steam. Moreover, the exhaust gas dischargedfrom the waste heat boiler 10 is directed to the stack 2.

Referring again to FIG. 1, the air-heating heat exchanger 5 is providedpartway along an air conditioner air supply passage 31 connecting ablower 29 to an air conditioner 30, and carries out heat exchangebetween air that is to be supplied to the air conditioner 30 from theblower 29 and the exhaust gas directed from the stack 2. The air heatedby exchanging heat with the exhaust gas is fed via a filter 32 into theair conditioner 30 from the air-heating heat exchanger 5.

One end of a bypass 34 is connected to the air conditioner air supplypassage 31 via switchover means 33 between the blower 29 and theair-heating heat exchanger 5, and the other end of the bypass 34 isconnected to the air conditioner air supply passage 31 between theair-heating heat exchanger 5 and air conditioner 30.

The switchover means 33 can switch over between a first state in whichthe air from the blower 29 is made to flow toward the bypass 34 and asecond state in which the air from the blower 29 is made to flow towardthe air-heating heat exchanger 5. The first state is selected when theoutside air temperature is comparatively high, and the second state isselected when the outside air temperature is comparatively low. That is,the bypass 34, which bypasses the air-heating heat exchanger 5 andswitches over between opened and closed states according to the outsideair temperature, is connected, on either side of the air-heating heatexchanger 5, to the air conditioner air supply passage 31 connected tothe air conditioner 30.

The exhaust gas that has undergone heat exchange in the air-heating heatexchanger 5 is discharged to the outside through the stack 7 via thewaste-water-heating heat exchanger 6. Supplied by a pump 35 to thewaste-water-heating heat exchanger 6 is waste water generated in thepure water generator 26 for generating the pure water that is to besupplied to the waste heat boiler 10. This waste water is heated in thewaste-water-heating heat exchanger 6 by heat exchange with the exhaustgas discharged from the air-heating heat exchanger 5.

The exhaust gas is cooled by heat exchange with air in the air-heatingheat exchanger 5, and part of the water contained in the exhaust gas iscondensed by this cooling and discharged as drain water from theair-heating heat exchanger 5. The exhaust gas is cooled by heat exchangewith waste water in the waste-water-heating heat exchanger 6, and partof the water contained in the exhaust gas condenses within thewaste-water-heating heat exchanger 6 and is discharged as drain waterfrom the waste-water-heating heat exchanger 6.

The drain water from the air-heating heat exchanger 5 and thewaste-water-heating heat exchanger 6 is then recovered by drain waterrecovery/supply means 36, and the drain water thus recovered is suppliedby the drain water recovery/supply means 36 to an air conditioner airhumidifier 37 or a hot water washer 38 for washing a vehicle body aftercompletion of painting, which are appliances requiring comparativelyhigh temperature water.

The drain water recovery/supply means 36 includes a pipeline 40 fordirecting the drain water from the air-heating heat exchanger 5 and thewaste-water-heating heat exchanger 6, a first tank 41 to which thepipeline 40 is connected and to which the waste water heated in thewaste-water-heating heat exchanger 6 is directed, a branch pipeline 43,one end of which is connected to the pipeline 40 partway along via athree-way valve 42, a second tank 44 to which the other end of thebranch pipeline 43 is connected, a first pump 47, the intake side ofwhich is connected to the first tank 41 and the discharge side of whichis connected to the hot water washer 38 via a filter 45 and a three-wayvalve 46, a second pump 48, the intake side of which is connected to thesecond tank 44, and a pipeline 50 connected to the discharge side of thesecond pump 48 via a filter 49. The pipeline 50 is connected to aplurality of nozzles 51, 51 of the air conditioner humidifier 37disposed within the air conditioner 30 on the downstream side of thefilter 32. The discharge side of the first pump 47 is also connected tothe pipeline 50 via the filter 45 and the three-way valve 46.

In accordance with the drain water recovery/supply means 36 having theabove-mentioned arrangement, the drain water from the air-heating heatexchanger 5 and the waste-water-heating heat exchanger 6, and the wastewater from the pure water generator 26 can be mixed within the firsttank 41. The drain water generated from the exhaust gas is alkalinebecause ammonia has been sprayed into the exhaust gas in the denitrationdevice 16 of the generator system 1 and the steam generated in the wasteheat boiler 10 from pure water into which caustic soda has been injectedis supplied to the combustor 13, but its alkalinity is weakened bydilution due to mixing with the waste water from the pure watergenerator 26 within the first tank 41.

A fan 52 is attached to the air conditioner 30, and the humidified airfrom the air conditioner 30 is supplied by the fan 52 to automobilepainting equipment 53, etc. via an air-conditioning duct 54.

The operation of this embodiment is now explained. After the thermalenergy of the exhaust gas discharged from the turbine 11 of the gasturbine 8 is recovered in the waste heat boiler 10, if the open/closevalve 3 is open, the exhaust gas from the waste heat boiler 10 isdischarged though the stack 7 via the air-heating heat exchanger 5 andthe waste-water-heating heat exchanger 6.

In the air-heating heat exchanger 5, the air that is to be supplied tothe air conditioner 30 is heated by heat exchange with the exhaust gas,and in the waste-water-heating heat exchanger 6, the waste water fromthe pure water generator 26 is heated by heat exchange with the exhaustgas, thereby recovering the waste thermal energy from the gas turbine 8effectively.

Furthermore, in the air-heating heat exchanger 5, part of the watercontent in the exhaust gas is condensed by being cooled by heat exchangewith air directed to the air conditioner 30, the water content thuscondensed is discharged as comparatively high temperature drain waterfrom the air-heating heat exchanger 5, and the drain water istemporarily stored in the tank 41 or 44 of the drain waterrecovery/supply means 36. Moreover, in the waste-water-heating heatexchanger 6, part of the water contained in the exhaust gas is condensedby being cooled by heat exchange with the waste water, the water contentthus condensed is discharged as comparatively high temperature drainwater from the waste-water-heating heat exchanger 6, and the drain wateris temporarily stored in the tank 41 or 44 of the drain waterrecovery/supply means 36.

The comparatively high temperature drain water within the tank 41 or 44is supplied to the nozzles 51, 51 of the air conditioner humidifier 37by the pump 47 or 48 so as to humidify the air fed into the airconditioner humidifier 37, thus avoiding a decrease in the temperatureof air-conditioning air and thereby further improving the efficiency ofrecovery of the waste thermal energy from the gas turbine 8. That is,simply adding room temperature water causes the temperature of theair-conditioning air to decrease, but by using comparatively hightemperature drain water for humidification a decrease in the temperatureof the air-conditioning air can be avoided.

The drain water recovered from the air-heating heat exchanger 5 can alsobe utilized in the hot water washer 38, which is an appliance requiringcomparatively high temperature water, thus avoiding the consumption ofextra energy. That is, when room temperature water is used, a heater isneeded, but since comparatively high temperature drain water can besupplied, it is possible to avoid consuming extra energy, therebyfurther improving the efficiency of recovery of the waste thermalenergy.

In this way, the drain water generated from the exhaust gas is recoverednot only in the air-heating heat exchanger 5, but also in thewaste-water-heating heat exchanger 6 on the downstream side of theair-heating heat exchanger 5, and it is therefore possible to recoverwater contained in the exhaust gas more effectively, thereby furtherimproving the efficiency of recovery of the waste thermal energy.

Moreover, the waste water heated by the waste-water-heating heatexchanger 6, and the drain water from the air-heating heat exchanger 5and the waste-water-heating heat exchanger 6 can be mixed in the tank 41of the drain water recovery/supply means 36. Because of this, althoughthe drain water generated from the exhaust gas is alkaline, since it isdiluted within the tank 41 by mixing with the waste water from the purewater generator 26, the alkalinity is weakened, and the water within thetank 41 can be utilized effectively in more appliances, such as the hotwater washer 38, in addition to the air conditioner humidifier 37,thereby extending the applications.

Furthermore, since the bypass 34 bypassing the air-heating heatexchanger 5 and switching over between opened and closed statesaccording to the outside air temperature is connected, on either side ofthe air-heating heat exchanger 5, to the air conditioner air supplypassage 31 connected to the air conditioner 30, changes according to theseason in the amount of drain water and the air conditioner temperaturerequired by the air conditioner humidifier 37 and the hot water washer38 can be accommodated easily.

Moreover, the humidified air acquired by the air conditioner 30 issupplied to the automobile painting equipment 53 by the fan 52, and thedrain water from the air-heating heat exchanger 5 and thewaste-water-heating heat exchanger 6 can be utilized more effectively inthe automobile painting equipment 53, in which it is important tomaintain the temperature and the humidity constant.

Furthermore, since part of the steam acquired by the waste heat boiler10 is supplied to the combustor 13 of the gas turbine 8, by increasingthe weight of gas fed to the turbine 11 via the combustor 13 andincreasing the rotational speed of the turbine 11, the capacity of thegenerator 9 can be increased, and the steam returned to the gas turbine8 side can be recovered effectively as drain water.

Although an embodiment of the present invention is explained in detailabove, the present invention is not limited to the above-mentionedembodiment and can be modified in a variety of ways without departingfrom the present invention described in the scope of the claims.

For example, in the above-mentioned embodiment, the prime mover drivingthe generator 9 is the gas turbine 8, but it is not limited thereto, andit may be a diesel engine. Furthermore, the humidified air from the airconditioner 30 can be used for heating each floor in a factory.

Moreover, in the above-mentioned embodiment, the waste-water-heatingheat exchanger 6 is connected in line to the downstream side of theair-heating heat exchanger 5, but the air-heating heat exchanger 5 andthe waste-water-heating heat exchanger 6 may be connected in parallel.

1. A cogeneration system that includes a prime mover (8) for obtainingpower for driving a generator (9) by combustion of a fuel, a waste heatboiler (10) for recovering thermal energy from exhaust gas dischargedfrom the prime mover (8), and an air-heating heat exchanger (5) forheating air that is to be fed into an air conditioner (30) by heatexchange with the exhaust gas discharged from the waste heat boiler(10), characterized in that the system comprises drain waterrecovery/supply means (36) capable of recovering drain water generatedfrom the exhaust gas cooled by heat exchange in the air-heating heatexchanger (5) with the air that is to be fed into the air conditioner(30) and supplying the drain water thus recovered to an appliance (37,38) that requires comparatively high temperature water.
 2. Thecogeneration system according to claim 1, wherein the system furthercomprises a pure water generator (26) for generating pure water forsupply to the waste heat boiler (10), and a waste-water-heating heatexchanger (6) for heating waste water from the pure water generator (26)by heat exchange with the exhaust gas discharged from the waste heatboiler (10), the drain water recovery/supply means (36) comprising atank (41) in which the waste water heated by the waste-water-heatingheat exchanger (6) and the drain water are mixed.
 3. The cogenerationsystem according to claim 2, wherein the drain water recovery/supplymeans (36) is arranged so as to be able to recover drain water generatedfrom the exhaust gas cooled by heat exchange with the waste water in thewaste-water-heating heat exchanger (6), and to supply the drain water tothe appliance (37, 38).
 4. The cogeneration system according to eitherclaim 2 or 3, wherein a bypass (34), which bypasses the air-heating heatexchanger (5) and switches over between opened and closed statesaccording to the outside air temperature, is connected, on either sideof the air-heating heat exchanger (5), to an air conditioner air supplypassage (31) connected to the air conditioner (30).
 5. The cogenerationsystem according to either claim 1 or 3, wherein the appliance is an airconditioner air humidifier (37).
 6. The cogeneration system according toeither claim 1 or 3, wherein the appliance is a hot water washer (38).7. The cogeneration system according to anyone of claims 1-3, whereinthe waste heat boiler (10) is connected to a combustor (13) of a gasturbine, which is the prime mover (8), to thereby supply a part of steamacquired by the waste heat boiler (10) to the combustor (13).